Rotary vibrator

ABSTRACT

A rotary vibrator in which energy from a rotating shaft is converted to mechanical vibrations between a rotor member and a stator member, one of which is formed as a prism the crosssection of which is a regular polygon with rounded vertices while the other is provided with a plurality of balls or rolls axially parallel to the prism, retained in such relative positions that they are positioned at the vertices of a regular polygon the face number of which differs from the face number of the prism, preferably by one.

United States Patent Poulsen [54] ROTARY VIBRATOR [72] Inventor: Peder Ulrik Poulsen, Lonholt Ladegaard 3480 Fredensborg, Lyngby, Denmark [22] Filed: Dec. 9, 1969 [2]] Appl. No.: 883,434

[30] Foreign Application Priority Data Dec. I0, 1968 Denmark ..6047

[ 52] 1.8. CI. ..259/l R, 259/DIG. 42

511 1m. (:1. .1101: 11/00 581 Field of Search ..2s9/1,1 1o.42,1 1o.44

[56] References Cited uumzo STATES PATENTS I 2,490,122 12/1949 Glegg .1 .1259/DlG. 42

[4 1 May 9,1972

FOREIGN PATENTS OR APPLICATIONS 1,428,728 1/1966 France ..259/DlG. 42

Primary Examiner-Walter A. Scheel Assistant Eramirrer-Alan l. Cantor Attorney-Waters, Roditi, Schwartz 8t Nissen [57] ABSTRACT 9 Claims, 4 Drawing Figures ROTARY VIBRATOR This invention relates to a rotary vibrator in which energy from a rotating shaft is converted to mechanical vibrations between a rotor member and a stator member, one of which is formed as aprism the cross-sectionof which presents a regular polygon with rounded verticeswhile the other is provided'with a plurality of balls or rolls. axially parallel to the prism, retained in such relative positions that they are positioned at the vertices of a regular polygon'the face number of which differs from the face number of the prism, preferably by one.

The vibrations, generatedby a vibrator of this type maybe transmitted to various materials, for instance solid bodies, powderedmaterials, or liquids. The vibrations may be transmitted either by direct contact with the vibrator or they may be led indirectly through rigid vibration-transmitting elements to the material or bodies tobe vibrated.

In a normally used type of rotary vibrator the vibrations are generated by providing a rapidly rotating-shaft suspended at both ends with a load positioned eccentrically with respectto the shaft andrigidly connected thereto. The centrifugal force will here produce the desired vibrations at aifrequency corresponding to the number of revolutions transmitted to the vibrator shaft.

In another commonly used type, the vibrator shaft isprovided with a journal positioned eccentrically with respect to the shaft or a crank connected by a connecting rod with the body to be vibrated, which may for instance be a shaking or flow table or the bottom of a liquid container. In this construction the amplitude of the vibrations transmitted to the shaft will correspond to the crank stroke, but by the insertion of a suitable resilient element the amplitude, as in the first described type, is made dependent on the mass of the vibrated body and the ratio of the vibration frequency tothe natural vibration figure of the system.

For several reasons it may be desirable to have relatively high frequency magnitudes in the said vibrators, and thisin many cases causes difficulties. To couple the vibrator shaft directly to-the drivingmotor is the most expedient form of power transmission, but in many. cases the reliable andinex-v pensive squirrel-cage motors are preferred atithe energy source, and this limits theoutput to theACfrequency, themaximum of which is about 3,000 rpm. Where motor types with higher numbers of revolutions are used, the result will usually be a less reliable system, in that the Iifeofthe motor and the vibrator shaft bearings will be reduced considerably by an increase of the speed of revolution. The same difficulty is experienced when using a gearing for increasing the, speed of revolution, because this is a cost-increasinglink that nor mally requires specific maintenance.

The prior art describes an apparatus for the generation of regular vibrations of a higher frequency than that of the vibrator shaft which depends on the number of revolutions. But that apparatus is adapted for impulse excitation, contrary to the sinusoidal vibrations generated by the previously cited prior art. The impulse excitation apparatus, however, never became very popular because they were found to be shortlived on account of the mechanical impact to bearings and other parts.

It is an object of the present invention to provide a rotary vibrator which generates non-shock, sinusoidal vibrations of higher frequency than the vibrator shaft.

This object has been accomplished by forming the rotor member and the stator member relatively to one another so as to provide a high approximation of contact between each of the balls or rolls and the prism in anyangular position of the said members relatively to one another. The vibrations excited in this manner are smooth. and can be transmittedby means of a connecting rod or in any other convenient manner to the body to be vibrated. The frequency of thevibrations will be a multiple of the number of revolutions of the. shaft, and the multiplication factor will be. within the range of 2 to 10 or above, determined by the .further adaptation of the rotary vibrator, including the number of faces of the prism and the polygon. In this manner vibrations of frequencies between I and, 500'I-lz or more can be obtained by direct coupling to a short circuit motor making for instance 300 rpm.

By providing the prism with sides of concave or convex cross-section it will be possible to obtain a particularly high degree of contact between the prism and the rolls or balls in any angular position of the stator and rotor members relative to one another. In fact it is possible to obtain complete contact similar to that of a ball or roller bearing. Whether the sides of the prism are convex or concave and the degree of convexity or concavity depend on a number of factors, such as the numberof faces of the prism and the polygon and the diameters of the rolls or balls.

The invention will be explained in greater detail here with reference to the drawing, in which FIG. 1 shows a vibrator element according to one embodiment of the invention,

FIG. 2. illustrates a second embodiment of the invention,

FIG. 3 illustrates in reduced scale, a rotary vibrator mounted on a connecting rod which is connected to a shaking or flow. table,

and FIG. 4. illustrates a modification of the embodiment of FIG. 2.

The vibrator shaft 1 is in FIG. 1, formed as a rotationally symmetrical prism of a cross-section approximately like a regular heptagon with rounded vertices. Around the prism six rolls 2 are mounted rotatably on their respective shafts 3, and the six shafts are mounted on a plate 4, of which only a section is indicated here, so that the centers of the shafts are disposed atthe respectivevertices of a regular hexagon. As a result of the geometrical principle on which the invention is based, it is possible by a suitable design of the rotationally symmetrical prism, the faces of which may be convex or concave, and a suitable selection ofrolldiameters and distances, to obtain with an extremely' high approximation the desired contact between each'roll and the prismface. The distance from the inscribedcircle of the roll system to the prism center being greater at Sthanat 6, .the rotation of the prism about a fixed axis at a constant angular speed simultaneously with a constant orientation of the roll system will cause translation to the roll system whereby its center is made to perform a smooth circular movementabout the-prism axis, as indicated by the circle 7. Theposition illustrated in the figure is repeated each time the prism has performed one seventh of a revolution,,and thus it will be seen that the movement of the plate 4 and the components associated therewith is identical with the movement that would be obtained in a conventional system with an eccentricity equal to the radius of the circle 7. However the effeet in a vibrator according to the invention will be achieved by one seventh of the number of revolutions required in the conventional system. With 3,000 rpm in the embodiment illustrated here it will therefore be possible to obtain a frequency of 350 cps.

Tests with many different prisms with different numbers of sides and shapes showthat an effect as here described can be achieved under the following conditions: Where the prism has an odd number of sides the number of rolling bodies shall be even, and where the prism has-an even number of sides there shall be an odd number of rolling members, provided that the number of rolling members should in both cases preferably be one higher or one lower than the number of sides of the prism.

- An analogous evaluation will show that a corresponding effect can be achieved where the roll system is applied in connection with the internal surface of a hole the cross-section of which is fonned approximately as the corresponding prism.

The multiplication factor in the embodiment illustrated in FIG. 1 will be equal to the number of sides of the prism.

The embodiment of the invention illustrated in FIG. 2 differs from the embodiment described above in that the rolls are mounted in a common holder 8 and outwardly controlled by a ring 9. On rotationof the prism 10 the roll holder will rotate in r the same direction but at approximately half the angular speed of the prism. This construction will therefore be analogous with that of a conventional roller bearing and will be equally simple and robust. However, on account of the natural rotation of the roll system, the multiplication factor will be lower than in the embodiment shown in FIG. 1, and it will be readily seen that the factor with a number of prism sides n will be about n+l/2. FIG. 4 is similar to FIG. 2 and the same reference numerals with the suffix a have been applied thereto. However, in FIG. 4 the prism sides are convex, whereas in FIG. 2 they are concave. The construction shown in FIG. 3 is similar to a ball or roller bearing and comprises an outer race 9', a ball or roll holder 8' and an inner race 10 formed as a prism with the number of faces equal to 9, and the multiplication factor will consequently in this case be about 5. FIG. 3 exemplifies the mounting of the vibrator according to the invention. The inner race 10 is here mounted on the shaft of a motor (not shown) and the outer race is pressed into a connecting rod 12, the other end of which is secured to a plate 13 which is to be vibrated. The plate 13 may for instance be a shaking table or flow table or the bottom of a liquid container. As the outer vibrator race performs a circular movement, the connecting rod, besides the vertical sinusoidal oscillation, is caused to perform a slight angular oscillating movement, but this will normally be without significance or it will be equalized by the components, and nonnally it will therefore not be necessary to mount the upper end of the connecting rod rotatably.

It will be obvious that many other applications of the vibrator in which the relative movements of prism and outer race are utilized are conceivable within the scope of the invention.

What I claim is:

l. A rotary vibrator comprising a rotating shaft, a rotor member coupled to said shaft and a stator member, one of said members being formed as a prism the cross-section of which is a regular polygon with rounded vertices while the other of said members includes a plurality of elements of circular cross-section having an axis of rotation axially parallel to the prism and retained in such relative positions that they are positioned at the vertices of a regular polygon the face number of which differs from the face number of the prism, the rotor member and the stator member being formed relatively to one another so as to maintain a high degree of contact between each of the elements and the prism in any relative angular position of the said members.

2. A rotary vibrator according to claim 1, wherein the faces of the prism are convex.

3. A rotary vibrator according to claim 1, wherein the faces of the prism are concave.

4. A rotary vibrator according to claim 1, wherein the elements are balls.

5. A rotary vibrator according to claim 1, wherein the elements are rolls.

6. A rotary vibrator according to claim 1, comprising a common holder supporting said elements.

7. A rotary vibrator according to claim 1, comprising an outer race encircling said elements.

8. A rotary vibrator according to claim 7, wherein the prism is an inner race.

9. A rotary vibrator according to claim 1 wherein the face numbers differ by one. 

1. A rotary vibrator comprising a rotating shaft, a rotor member coupled to said shaft and a stator member, one of said members being formed as a prism the cross-section of which is a regular polygon with rounded vertices while the other of said members includes a plurality of elements of circular cross-section having an axis of rotation axially parallel to the prism and retained in such relative positions that they are positioned at the vertices of a regular polygon the face number of which differs from the face number of the prism, the rotor member and the stator member being formed relatively to one another so as to maintain a high degree of contact between each of the elements and the prism in any relative angular position of the said members.
 2. A rotary viBrator according to claim 1, wherein the faces of the prism are convex.
 3. A rotary vibrator according to claim 1, wherein the faces of the prism are concave.
 4. A rotary vibrator according to claim 1, wherein the elements are balls.
 5. A rotary vibrator according to claim 1, wherein the elements are rolls.
 6. A rotary vibrator according to claim 1, comprising a common holder supporting said elements.
 7. A rotary vibrator according to claim 1, comprising an outer race encircling said elements.
 8. A rotary vibrator according to claim 7, wherein the prism is an inner race.
 9. A rotary vibrator according to claim 1 wherein the face numbers differ by one. 